BOH,

did exactly the same last week. Took the kids to Cirque Du Soleil in Berlin, out on the 1st and back on the 4th. 2 adults and 2 kids on any BA flight was £1800, and with EZY was £467.

BA fly into TXL which is not that much closer than EZY into Schoenefeld.

Good points of EZY

Price
Reasonably efficient
On time

Bad Points

Scrum at check in (no queue mgt and I picked the Q with the transvestite who chose to have a 20 min argument!!!)
They ran out of beer (and food, except the awful soup)!!! The stewardess asked me what it was with the Brits that we buy stuff on board. If she flies Berlin to Pisa then she said she could read the Bible, but LGW-Berlin she sells everything in sight.

For the price and the service you can't knock it. But I guess if BA get people to pay the £685 then good luck.

FYI, taxi from Shoenefeld into town is about 35 Euros, or you can take the train and get out at the Zoo (Zoological Gardens) and then try and figure out the Berlin subway system (makes you realise how wonderful the London Underground Map really is!)